1. Field of the Invention.
This invention relates to a device for preventing the formation of vapor lock in two-cycle engines.
2. Description of the Prior Art.
Vapor lock is a commonly encountered problem in two-cycle engines. Vapor lock occurs when fuel is inhibited from passing through the fuel line to the engine due to the presence of vaporized fuel in the fuel pump and along the fuel line. When vapor lock occurs the engine is fuel stained and will not run. Vaporization is caused by high temperatures around the fuel pump and fuel line which can result from heat migrating from the cylinders of the engine.
Numerous devices have been disclosed which are designed to maintain a reduced temperature about fuel lines in order to prevent the formation of a vapor lock. For example, U.S. Pat. No. 4,072,138 to Hawkins discloses a fuel systems having a heater mounted between the carburetor and the fuel pump. The heater is operated by circulating hot water from the engine block through the heater which is positioned next to the fuel line. To prevent vapor lock, a cooler is provided between the fuel pump and the heater. The cooler is operated by passing the fuel line in front of the radiator and exposing it to air currents passing to the radiator.
Another method for reducing the temperature of the fuel in the fuel system is disclosed by U.S. Pat. No. 3,332,476 to McDougal. The device is designed to dissipate heat from the intake manifold by circulating vaporized liquid through an evaporater which is positioned next to the fuel line. The liquid in the evaporater absorbs the heat within the fuel line and vaporizes. The vapor is then transported to a cooler region in the engine where it is condensed and returned to the evaporater.
Evaporization of water has also been used to reduce the temperature of the fuel within the fuel system. U.S. Pat. No. 2,791,186 to Alden discloses a water jacket which is mounted about the fuel pump chamber. The water jacket is constructed of a porous metal surface which is kept wet through the use of a water reservoir and feed line. The nature of the porous surface permits water vapor to easily evaporate therefrom after absorbing heat from the pump chamber, thus reducing the temperature within the fuel system. Similarly, U.S. Pat. No. 2,120,779 to Ericson utilizes a cooler having a comparable porous surface which is fed by a water reservoir. The Ericson device is designed to evaporate water quickly by mounting the cooler in the direct path of the fan blast and away from heated parts of the engine, such as the exhaust manifold. Both the Alden and Ericson devices require the replenishment of water within the reservoir in order to operate over an extended period of time.
A variation of the water cooled fuel systems is disclosed by U.S. Pat. No. 4,084,564 to Rickert. The Rickert device uses a fuel circulating system which cools the fuel line through the use of a heat conveying tube. Cooler fuel from the fuel tank is circulated through the heat conveying tube which is positioned next to the fuel system. The heat conveying tube is constructed of heat conductive material which permits the fuel within the fuel system to be cooled by the fuel within the heat conveying tube.
Cooling ribs are provided in U.S. Pat. No. 2,834,469 to Mitterer for condensing vaporized fuel within the fuel line. The cooling ribs are mounted within a Venturi tube which is directly attached to the fuel line. As fuel passes through the fuel line, vaporized fuel passes into the Venturi tube where the cooling ribs cause it to condense. The condensed fuel is then returned in a liquid state within the fuel line at a lower temperature.
The devices previously disclosed for reducing the occurrence of vapor lock in two-cycle engines are relatively expansive, requiring extensive tubing and support structure to carry cooling fluid throughout the fuel delivery system.
The present invention provides several desireable features not found in the prior art, for example, it is simple and inexpensive. The fuel pump is thermally isolated (spaced) from the heat producing and heat transfer areas of the engine, including the carburetor. The fuel pump, which still is operated by conventional mechanical or impulse means, preferably is placed in the cool incoming airflow generated by the flywheel fan. This cool air acts as an additional thermally isolating layer over the fuel pump. Additional cooling means may be provided by placing the fuel pump in the fuel tank such that the fuel pump is thermally isolated from the heat providing areas of the engine.
The use of isolating materials in the fuel pump mounting strap prevent heat migration from the hot cylinder of the engine. As an added feature, isolation of the fuel pump allows for a larger, more effective air filter to be used, resulting in longer engine life and lower operating noise levels.